U.S. patent application number 10/831822 was filed with the patent office on 2005-10-27 for fast call set-up for multi-mode communication.
This patent application is currently assigned to MOTOROLA, INC.. Invention is credited to Dorenbosch, Jheroen P., Gipson, Jack A., Idnani, Ajaykumar R..
Application Number | 20050239498 10/831822 |
Document ID | / |
Family ID | 35137136 |
Filed Date | 2005-10-27 |
United States Patent
Application |
20050239498 |
Kind Code |
A1 |
Dorenbosch, Jheroen P. ; et
al. |
October 27, 2005 |
Fast call set-up for multi-mode communication
Abstract
Fast call set-up for a call to a multi-mode communication unit
(102) is facilitated by a method and apparatus for registering and
re-registering priorities with a SIP registrar (111). A list of
contacts with first priorities associated with a mode of operation
in a first enterprise network (106) is established and used. A
switch to second priorities is made when a probability of a switch
from the first mode of operation to a second mode of operation in a
second cellular network (108) satisfies a threshold. The list of
contacts includes a contact having an expiration time for the first
mode of operation. A quality factor is determined and the list of
contacts is re-registered and the expiration time changed if the
quality factor does not satisfy a threshold.
Inventors: |
Dorenbosch, Jheroen P.;
(Paradise, TX) ; Gipson, Jack A.; (Fort Worth,
TX) ; Idnani, Ajaykumar R.; (Schaumburg, IL) |
Correspondence
Address: |
POSZ LAW GROUP, PLC
12040 SOUTH LAKES DRIVE
SUITE 101
RESTON
VA
20191
US
|
Assignee: |
MOTOROLA, INC.
|
Family ID: |
35137136 |
Appl. No.: |
10/831822 |
Filed: |
April 26, 2004 |
Current U.S.
Class: |
455/552.1 |
Current CPC
Class: |
H04W 88/06 20130101;
H04W 76/10 20180201 |
Class at
Publication: |
455/552.1 |
International
Class: |
H04B 001/38 |
Claims
1. A method for reducing a call setup time for a call setup to a
multi-mode communication unit, the method comprising: registering,
with a Session Initiation Protocol (SIP) registrar, a list of
contacts having first respective priorities associated with a first
mode of operation of the multi-mode communication unit; using the
first respective priorities when the multi-mode communication unit
is operating in accordance with the first mode of operation; and
modifying the list of contacts at the SIP registrar, with second
respective priorities associated with a second mode of operation of
the multi-mode communication unit when a probability of a switch
from operation in accordance with the first mode of operation to
operation in accordance with the second mode of operation satisfies
a threshold.
2. A method in accordance with claim 1, wherein the first
operational mode includes a LAN mode according to one of a wireless
connection and a wired connection, and the second operational mode
includes a cellular mode.
3. A method in accordance with claim 1, wherein each of the first
operational mode and the second operational mode include one or
more of a wireless LAN mode, a wired LAN mode, a cellular mode, and
a Publicly Switched Telephone Network PSTN mode.
4. (canceled)
5. A method in accordance with claim 1, wherein the second
respective priorities include a first priority of a first contact
associated with the first mode of operation equal to a second
priority of a second contact associated with the second mode of
operation.
6. A method for reducing a call setup time for a call setup to a
multi-mode communication unit, the call setup conducted in
accordance with a protocol, the method comprising: registering a
list of contacts with a Session Initiation Protocol (SIP) registrar
associated with the protocol, the list of contacts including a
first contact having a first expiration time associated with
operation according to a first mode of operation of the multi-mode
communication unit; determining a quality factor associated with
the first mode of operation; and re-registering the list of
contacts with the SIP registrar, the list of contacts including the
first contact having a reduced expiration time if the quality
factor does not satisfy a first predetermined quality
threshold.
7. A method in accordance with claim 6, further comprising:
re-determining the quality factor associated with the first mode of
operation before the expiration of the first expiration time to
provide a second quality factor; and re-registering the list of
contacts, wherein the first expiration time is increased if the
second quality factor exceeds a second predetermined quality
threshold.
8. A method in accordance with claim 6, further comprising
preparing for operation in accordance with a second mode of
operation if the quality factor does not satisfy the first
predetermined quality threshold.
9. A method in accordance with claim 6, further comprising changing
to operation in accordance with a second mode of operation if the
quality factor does not satisfy a second predetermined quality
threshold.
10. (canceled)
11. A method in accordance with claim 6, wherein: the first contact
further includes a first priority, and the list of contacts further
includes: a second contact having a second expiration time and a
second priority associated with operation according to a second
mode of operation of the multi-mode communication unit; and a third
contact having a third expiration time longer than the first
expiration time and a third priority associated with the operation
according to the first mode of operation of the multi-mode
communication unit, where the third priority is lower than the
first and the second priority.
12. An apparatus for reducing a call setup time associated with a
call setup in a multi-mode communication environment, the apparatus
capable of operating according to a protocol, the apparatus
comprising: a memory; and a processor coupled to the memory, the
apparatus capable of maintaining at least two contacts in a Session
Initiation Protocol (SIP) registrar, the processor configured to:
assign a first priority to a first contact associated with
operation according to a first operational mode and a second
priority to a second contact associated with operation according to
a second operational mode, wherein the assignment results in the
registration of the first contact and the second contact with the
SIP registrar with the assigned first priority and the second
priority respectively; detect an impending switch between the
operation according to the first operational mode and the operation
according to the second operational mode; and modify a relative
priority between the first priority and the second priority, the
modification resulting from one of modifying the first priority and
modifying the second priority, such that the first priority of the
first contact is not higher than the second priority of the second
contact when the impending switch is detected, wherein the
modification results in the modification of the first contact and
the second contact at the SIP registrar with the modified relative
priority.
13. An apparatus in accordance with claim 12, wherein the first
operational mode includes a LAN mode according to one of a wireless
connection and a wired connection, and the second operational mode
includes a cellular mode.
14. An apparatus in accordance with claim 12, wherein each of the
first operational mode and the second operational mode include one
of a wireless LAN mode, a wired LAN modes a cellular mode, and a
Publicly Switched Telephone Network PSTN mode.
15. (canceled)
16. An apparatus in accordance with claim 12, wherein the processor
is further configured to: assign a first expiration time to the
first contact associated with the operation according to the first
operational mode; and modify the first expiration time when the
impending switch is detected such that the modified first
expiration time is shorter than the first expiration time.
17. An apparatus in accordance with claim 16, wherein the processor
is further configured to: assign a second expiration time longer
than the first expiration time to the second contact associated
with operation according to the second operational mode when the
impending mode switch is detected.
18. An apparatus in accordance with claim 12, wherein the processor
is further configured to: assign the first priority and the second
priority such that the first priority is higher than the second
priority.
19. An apparatus for reducing a call setup time associated with a
call setup in a multi-mode communication environment, the apparatus
capable of operating according to a protocol, the apparatus
comprising: a memory; and a processor coupled to the memory, the
processor configured to: maintain a contact list in a Session
Initiation Protocol (SIP) registrar, the contact list containing at
least a first contact associated with operation according to a
first operational mode, the first contact having a first priority
and a first expiration time, and a second contact associated with
operation according to a second operational mode, the second
contact having a second priority and a second expiration time,
wherein maintaining the contact list results in the registration of
the first contact and the second contact with the SIP registrar
with the assigned first priority and the second priority
respectively; determine a quality factor associated with the first
operational mode; and modify the contact list at the SIP registrar
if the quality factor does not meet a predetermined quality level,
the modification resulting in at least one of: a third expiration
time for the first contact, the third expiration time being shorter
than the first expiration time and shorter than the second
expiration time, and a third priority for the first contact, the
third priority being not higher than the second priority.
20. An apparatus in accordance with claim 19, wherein the processor
is further configured to: re-determine the quality factor
associated with the first mode of operation to provide a second
quality factor; and re-modify the contact list if the second
quality factor meets a second predetermined quality level, the
re-modification resulting in at least one of: an expiration time
for the first contact, the expiration time being longer than the
third expiration time, and a priority for the first contact, the
priority being not lower than the second priority.
21. An apparatus in accordance with claim 19, wherein the
processor, in maintaining the contact list is further configured to
one of maintain the first priority, maintain the first expiration
time, maintain the second priority, and maintain the second
expiration time, wherein the maintained contact list further
includes one of the second expiration time being longer than the
first expiration time, and the second priority being lower than the
first priority.
Description
FIELD OF THE INVENTION
[0001] The present invention relates in general to wireless
communication units and wireless networks, and more specifically to
a method and apparatus for reducing a call set-up time for
multi-mode wireless communication units.
BACKGROUND OF THE INVENTION
[0002] Loosely coupled Wireless Local Area Networks (WLAN)
supported by WLAN servers, such as enterprise servers or the like,
in addition to providing a user with such amenities as high-speed
wireless Internet access to an expanding universe of services can
provide an inexpensive alternative for telephony services as well
as other real-time applications. A user can carry a wireless device
such as a subscriber unit, which may also be referred to
interchangeably from time to time herein as a communication unit,
or a multi-mode communication unit with multi-use, such as
dual-use, capability. Accordingly, the multi-mode communication
unit can provide voice communication over an enterprise WLAN server
when the multi-mode communication unit is in a WLAN and over a
cellular wide area network (WAN or cellular network) such as GSM or
3G when the multi-mode communication unit is outside of the WLAN or
leaving the WLAN. As noted, additional networks requiring
additional modes of operation may also be present.
[0003] When the multi-mode communication unit is linked or
otherwise connected through a wireless link or connection to a
first network, such as during a call or other communication over
the first network, and is moving within range of a second network
such as, for example, from a WLAN to a cellular network, a handover
of the call, and thus the link or connection, from the first
network to the second network is desirable. Handovers are
preferably conducted with minimal undesirable effects, service
degradation, or service interruption. Since preparation for making
a connection to a new network may take a relatively long time on
the order of, say 10s, for example to bring up software and
hardware necessary to operate within and register with the new
system, a user can experience unsatisfactory service or, worse, a
dropped call or link. Conversely, maintaining registration and
communication with multiple systems at all times can seriously
reduce battery life for the multi-mode communication unit, and may
create problems associated with the management of an excessive
number of registrations for multi-mode communication units which
may not be connected with a particular service. Thus maintaining
registration with more than one network when it is not necessary is
impractical and inefficient.
[0004] As will be appreciated, a main target market for multi-mode
equipment is the large enterprise. Employees using multi-mode
communication units can, for example, use the same phone in the
enterprise and in the cellular system. Preferably, the multi-mode
communication unit uses the Wireless IP LAN (WLAN) while the
employee is inside the enterprise giving significant cost savings
for the enterprise. In accordance with various exemplary
embodiments, operation of a multi-mode communication unit, in
switching between systems, should be transparent to a user. Thus,
when a user leaves or enters an enterprise, the multi-mode
communication unit should automatically switch modes from WLAN to
cellular or vice versa. It should be noted that notwithstanding the
need to switch systems or networks, inbound calls addressed to the
multi-mode communication unit must reach multi-mode communication
unit within a reasonable time regardless of its location.
[0005] Therefore, to address the above described problems and other
problems, what is needed is a method and apparatus for reducing a
call set up time for a call to a multi-mode communication unit
associated with switching between modes, such as the time
associated with setting up a new connection to a multi-mode
communication unit during or after switching between wireless
communications networks such as a WLAN and a cellular network.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006] The accompanying figures, where like reference numerals
refer to identical or functionally similar elements and which
together with the detailed description below are incorporated in
and form part of the specification, serve to further illustrate a
preferred embodiment and to explain various principles and
advantages in accordance with the present invention.
[0007] FIG. 1 is a diagram illustrating a simplified and
representative environment associated with an exemplary multi-mode
communication unit and exemplary wireless networks in accordance
with various exemplary embodiments;
[0008] FIG. 2 is a diagram illustrating an exemplary multi-mode
communication unit and exemplary wireless networks arranged for the
routing of a communications link to the appropriate one of two
wireless communications networks in accordance with various
exemplary embodiments;
[0009] FIG. 3 is a diagram illustrating an exemplary multi-mode
communication unit and exemplary wireless networks arranged after a
mode switch to a second wireless communications network in
accordance with various exemplary embodiments;
[0010] FIG. 4 is a diagram illustrating an exemplary multi-mode
communication unit arranged outside the range of wireless
communications networks in accordance with various exemplary
embodiments;
[0011] FIG. 5 is a block diagram illustrating portions of an
exemplary multi-mode communication unit in accordance with various
exemplary embodiments;
[0012] FIG. 6 is a block diagram illustrating portions of an
exemplary infrastructure device in accordance with various
exemplary embodiments;
[0013] FIG. 7 is a block diagram illustrating portions of an
exemplary registrar in accordance with various exemplary
embodiments;
[0014] FIG. 8 is a flow chart illustrating an exemplary
registration procedure in accordance with various exemplary and
alternative exemplary embodiments; and
[0015] FIG. 9 is a flow chart illustrating another exemplary
registration procedure in accordance with various exemplary and
alternative exemplary embodiments.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0016] In overview, the present disclosure concerns wireless
communications devices or units, often referred to as communication
units, such as cellular phone or two-way radios and the like having
multi-mode operating capability, such as a dual mode capability
understood as the ability to operate in accordance with two, or in
some cases more, operating modes such as an enterprise mode and a
cellular mode associated with a communication system such as an
Enterprise Network, a cellular Radio Access Network, or the like.
Such communication systems may further provide services such as
voice and data communications services to multi-mode communication
units. More particularly, various inventive concepts and principles
are embodied in systems, multi-mode communication units, and
methods therein for reducing a call set up time associated with a
call to a multi-mode communication unit. It should be noted that
the term communication unit or multi-mode communication unit may be
used interchangeably herein with subscriber unit, wireless
subscriber unit, wireless subscriber device or the like. Each of
these terms denotes a device ordinarily associated with a user and
typically a wireless mobile device that may be used with a public
network in accordance with a service agreement or within a private
network such as an enterprise network. Examples of such units
include personal digital assistants, personal assignment pads, and
personal computers equipped for wireless operation, a cellular
handset or device, or equivalents thereof provided such units are
arranged and constructed for operation in different networks.
[0017] The instant disclosure is provided to further explain in an
enabling fashion the best modes of performing one or more
embodiments of the present invention. The disclosure is further
offered to enhance an understanding and appreciation for the
inventive principles and advantages thereof, rather than to limit
in any manner the invention. The invention is defined solely by the
appended claims including any amendments made during the pendency
of this application and all equivalents of those claims as
issued.
[0018] It is further understood that the use of relational terms
such as first and second, and the like, if any, are used solely to
distinguish one from another entity, item, or action without
necessarily requiring or implying any actual such relationship or
order between such entities, items or actions.
[0019] Much of the inventive functionality and many of the
inventive principles when implemented, are best supported with or
in software or integrated circuits (ICs), such as a digital signal
processor and software therefore or application specific ICs. It is
expected that one of ordinary skill, notwithstanding possibly
significant effort and many design choices motivated by, for
example, available time, current technology, and economic
considerations, when guided by the concepts and principles
disclosed herein will be readily capable of generating such
software instructions or ICs with minimal experimentation.
Therefore, in the interest of brevity and minimization of any risk
of obscuring the principles and concepts according to the present
invention, further discussion of such software and ICs, if any,
will be limited to the essentials with respect to the principles
and concepts used by the preferred embodiments.
[0020] The communication systems and communication units of
particular interest are those providing or facilitating voice
communications services or data or messaging services over cellular
wide area networks (WANs), such as conventional two way systems and
devices, various cellular phone systems including analog and
digital cellular, CDMA (code division multiple access) and variants
thereof, GSM, GPRS (General Packet Radio System), 2.5G and 3G
systems such as UMTS (Universal Mobile Telecommunication Service)
systems, Internet Protocol (IP) Wireless Wide Area Networks like
802.16, 802.20 or Flarion, integrated digital enhanced networks and
variants or evolutions thereof. Furthermore the wireless
communication units or devices of interest have short range
wireless communications capability normally referred to as WLAN
capabilities, such as IEEE 802.11, Bluetooth, or Hiper-Lan and the
like preferably using CDMA, frequency hopping, OFDM or TDMA access
technologies and one or more of various networking protocols, such
as TCP/IP (Transmission Control Protocol/Internet Protocol), UDP/UP
(Universal Datagram Protocol/Universal Protocol), IPX/SPX
(Inter-Packet Exchange/Sequential Packet Exchange), Net BIOS
(Network Basic Input Output System) or other protocol structures.
Alternatively the wireless communication units or devices of
interest may be connected to a LAN using protocols such as TCP/IP,
UDP/UP, IPX/SPX, or Net BIOS via a hardwired interface such as a
cable and/or a connector.
[0021] As further discussed herein below, various inventive
principles and combinations thereof are advantageously employed to
reduce a call setup time during mode switching associated with a
multi-mode communication unit. A first list of contacts having
respective priorities for a first mode of operation, such as an
enterprise mode or the like, as would be typically associated with
the multi-mode communication unit may be established or otherwise
registered with, for example, a controller such as a network
controller, Session Initiation Protocol (SIP) registrar, SIP proxy
or server, enterprise server, enterprise PBX, or the like
preferably with wireless interface capabilities and capabilities to
connect and control calls or sessions through a Public Switched
Telephone System (PSTN). The first list is normally established or
registered when the multi-mode communication unit starts to operate
according to the first mode of operation, for example when it
powers up in a system supporting the first mode of operation or
when it roams into such a system and begins operations there.
[0022] The list of contacts may be modified with respective
priorities for a second mode of operation associated with the
multi-mode communication unit and the modified list may be
registered or re-registered. It will be appreciated by one of
ordinary skill in the art that the list of contacts with the first
respective priorities may be used when the multi-mode communication
unit is operating in accordance with a first mode of operation. The
modified list of contacts with the modified priorities may be
registered when a switch from operation out of the first network
and into another, such as the second network appears imminent. The
modified list may thus be used for contact with the multi-mode
communication unit prior to, during, and after when the transition,
mode switch, or the like, from operation in accordance with the
first mode of operation to operation in accordance with a second
mode of operation takes place. It will be appreciated that
determination of the impending transition from the first mode to
the second may occur prior to the actual mode switch by detecting
deteriorating signal quality, detecting a border cell, or the like
which suggest the likelihood of an impending mode switch.
Accordingly the registered contacts may be used after the
determination and prior to, during, or after the mode switch in
accordance with various exemplary embodiments. It will also be
appreciated that a probability associated with the impending mode
switch may be more clearly expressed as the probability of a mode
switch within an amount of time such as within the next 10 seconds
and may be determined in a manner to be described in greater
detail. In addition to determining a probability of a mode switch,
a simpler method such as the detection of a beacon signal or other
special indication associated with a border cell or border cells
placed at various locations along a service boundary of a service
area associated with the first mode may be used to signal an
impending mode switch without the explicit calculation of a
probability.
[0023] Further in accordance with exemplary embodiments, call setup
time during and after mode switching associated with a multi-mode
communication unit may be reduced by establishing or otherwise
registering a list of contacts with respective priorities
associated with a first mode of operation of the multi-mode
communication unit. The priorities may be used when the multi-mode
communication unit is operating in accordance with the first mode
of operation, such as an enterprise mode, WLAN mode or the like. A
second set of priorities associated with the list of contacts may
be used when a switch from operation in accordance with the first
mode of operation to operation in accordance with a second mode of
operation, such as a switch between the enterprise mode and a
cellular mode, is determined to be imminent.
[0024] Referring now to FIG. 1, a simplified and representative
exemplary scenario associated with reduction of call set up time
will be discussed and described. In accordance with various
exemplary embodiments, multi-mode communication unit 102 is movable
104 between service from a first wireless communications network
106 (hereinafter "first network 106") and service from a second
wireless communications network 108 (hereinafter "second network
108"). An exemplary arrangement in accordance with various
exemplary embodiments, better facilitates mobility by using a
Session Initiation Protocol (SIP) for managing session initiation
such as, for example, call setup. SIP is more fully described in
Internet Engineering Task Force (IETF) Request For Comments (RFC)
3261, available at www.ietf.org/rfc.html. In addition to providing
mobility, use of SIP improves availability of a single- or
multi-mode communication unit by allowing multiple contacts such as
addresses, telephone numbers, locations or the like, for the
communication unit to be registered or otherwise specified at a SIP
registration entity, such as SIP registrar 111. While the primary
placement of SIP registrar 111 is shown within first network 106,
it will be appreciated that SIP registrar may be located within
network switching function 110, within the second network 108, or
outside first network 106 and second network 108. It should be
noted that SIP registrar 111 is preferably a server configured to
accepts REGISTER requests for contact information that multi-mode
communication unit 102 or an entity associated therewith such as a
Home Location Register (HLR) wishes to be known. The information is
placed into the location service for SIP registrar 111's
domain.
[0025] As noted, a set of contacts represent where multi-mode
communication unit 102 can be reached such that an incoming call
can be quickly routed. For example, one contact can have an address
such as a mobile telephone number, an Internet address or the like
for providing contact with the multi-mode communication unit at the
WLAN and another contact can have an address such as a mobile
telephone number, Internet address, Universal Resource Identifier
(URI), or the like for providing contact with the multi-mode
communication unit within the cellular network. One or more
additional contacts can be added to route the incoming call to a
service such as a pager, email, voice mail, or the like, if higher
priority contacts fail to result in a successful contact. It will
further be appreciated that the incoming call may be part of a
forwarded call from outside the WLAN and cellular environment.
Different contacts registered, for example, in SIP Registrar 111 or
otherwise specified, may further have different priorities or
q-values such that each contact will be tried in a well defined
order. It will further be appreciated that while the mere use of
different q-values is not uncommon within the SIP environment, the
particular techniques used for multi-mode communication units
described in further detail herein below go beyond conventional SIP
implementations. According to an exemplary call set-up in the SIP
environment, contact addresses are tried in an order of decreasing
q-value. Only after a contact attempt fails to reach multi-mode
communication unit 102 on a contact with a higher priority, are any
lower priority contacts tried. Contacts are tried until the call
set-up attempt succeeds on one of the contacts or until the call
set-up attempt fails completely.
[0026] First network 106 includes a network switching function 110
alternatively referred to as Private Branch Exchange (PBX),
enterprise server, media gateway controller (MGC), IP-PBX, and so
on. The WAN or second network 108 also includes a network switching
function, alternatively referred to as a mobile switching center or
MSC 112. The coverage area of second network 108 is typically much
larger than that of first network 106 and may overlap in total or
in part the coverage area of first network 106 as depicted. Note
that although the terms first and second networks are used in an
exemplary fashion throughout the description the terms may be
interchanged, e.g. first network 106 could be a WAN and second
network 108 a WLAN, or both could be WLANs or WANs for example. It
will also be appreciated that entities or functions associated with
typical networks are not specifically shown but understood to be
present and operational. For example first network 106, may use a
large number of Access Points, not shown, to support a radio or
wireless link with multi-mode communication unit 102. Further,
typical network routing equipment such as servers, concentrators,
routers, are not shown but assumed to be present where appropriate
as would be appreciated by one of ordinary skill in the art.
Similarly, second network 108 or wireless WAN (hereafter WAN)
typically includes a plurality of base transmitters, antenna
towers, and base site controllers all serving to provide a radio
access network for communication units as well as various
registrars, billing servers and so forth, all of which are not
shown. It will be appreciated that wireless signals 105 and 107
represent signal coverage between multi-mode communication unit 102
and first network 106 and second network 108 respectively.
[0027] While first and second networks 106, 108 are referred to
herein as wireless networks, portions of these networks or
respective elements thereof may be interconnected or coupled using
terrestrial based media such as optical fiber or wires. For
example, the switching functions 110 and 112 may be coupled to a
wider balance of respective network components or nodes using
ordinary cables or wires. Furthermore first network 106 can include
and support voice services for stationary or static communications
units also capable of being coupled to the network using
conventional cabling or wires. Thus the discussions below will
refer alternatively to the first network 106 as a WLAN or LAN.
[0028] Both first and second networks 106 and 108, via the network
switching functions 110 and 112, can likely be interconnected to or
via a public switched telephone and data network and, in a
preferred embodiment, are packet data networks using packet
switched methodologies, and thus coupled to each other. First and
second networks 106 and 108 preferably use an exemplary protocol
for setting up sessions or connections with other units. Various
known protocols can be used, such as H.323 defined and promulgated
by the International Multimedia Telecommunication Consortium (IMTC)
(see http://www.imtc.org/h323.htm and associated websites for
descriptive documents) or Session Initiation Protocol (SIP)
defined, as noted above, by the Internet Engineering Task Force
(IETF) in RFC3261 document. Much of the discussion below, where
relevant, will assume that SIP and SIP constructs and entities are
being utilized in the WLAN and that legacy cellular or dispatch
protocols are being utilized in the WAN, where it is understood
that similar functions and methods are available using other
protocols if desired.
[0029] The network switching function 110 may serve a single
enterprise location, such as an office building or may serve
multiple enterprise sites, possibly located in different cities.
The network switching function 110 or enterprise server may serve a
WLAN hotspot such as a wireless access point (AP) or the like, or
multiple WLAN hotspots. It may also serve one or more WLAN coverage
areas in private homes that may be connected to the network
switching function 110 by such means as IP broadband connections.
Moreover, the network switching function 110 can be located at many
different locations, such as inside an enterprise, within a
broadband operator's premises, or at a Centrex location shared by
multiple enterprises, hotspots and/or homes. Generally, network
switching function 110 operates to establish a connection or to set
up a call such as connection 120-135 between wireless communication
units within the WLAN, such as multi-mode communication unit 102
and peer communication units, such as peer communication unit 114.
Communication from multi-mode communication unit 102 is preferably
according to packet data type communication and communication from
peer communication unit 114 will depend on its particular nature.
For example, if peer communication unit 114 is another static or
wireless communication unit within the WLAN or LAN, or first
network 106, communication may proceed according to packet data
communications, while if peer communication unit 114 is an ordinary
phone outside the LAN or WLAN, or first network 106, a circuit
switched connection is likely to be the mode of communication.
[0030] Other network entities specifically depicted include
mobility manager 116 and an optional proxy server 118. Mobility
manager 116 operates to facilitate handover activities, for
example, from first network 106 to second network 108, or vice
versa, when required. Proxy server 1118, as will be understood to
those of ordinary skill in the art, if present, generally provides
a central point of contact for communication units to contact when
a call set up or other connection is desired with or by a WLAN
communication unit. Proxy server 118 will have the most up to date
location information, such as addresses for communication units
within its purview, and can provide an intermediary function for
network switching function 110 in accordance with known techniques.
It should be noted that functions associated with proxy server 118
can be combined with mobility manager 116, or each can be a
stand-alone entity. Alternatively, functionality associated with
proxy server 118 and mobility manager 116 may be combined with
network switching function 110. For reasons that will be become
apparent, it may be advantageous to combine mobility manager 116
and proxy server 118. It will be appreciated that any combination
of the functionality of mobility manager 116 and proxy server 118
can be implemented as incremental software programs operating or
executing on the same network based computing platform as proxy
server 118.
[0031] To better illustrate call set up in accordance with various
exemplary embodiments, a session initiation by peer communication
unit 114 to, for example, multi-mode communication unit 102 is
shown. In one embodiment the signaling portion of the communication
including setup, control, and teardown, is preferably done using
SIP messaging while the bearer or content path 120-135 includes
voice or data carried using VoIP (voice over IP) techniques and
real time protocol (RTP) and User Datagram Protocol (UDP). It will
be assumed for illustrative purposes that at a time of power up of
peer communication unit 114, a first list of contacts has been
registered by multi-mode communication unit 102, for example, with
SIP registrar 111 according to descending priorities as noted
herein above and that the contact associated with first network
106, or the WLAN is preferably the address or contact number
associated with the highest priority contact registered with SIP
registrar 111 for contacting multi-mode communication unit 102.
[0032] When peer communication unit 114 sets up a call or initiates
a session with multi-mode communication unit 102, the call is
directed to a SIP Universal Resource Identifier (URI) associated
with multi-mode communication unit 102. Alternatively, peer
communication unit 114 may direct its call to a phone number of the
multi-mode communication unit 102 which is configured to terminate
at network switching function 110, or which is forwarded or
transferred to switching function 110 by the PSTN or switching
function 112 of second network 108. A call setup request will
consequently be routed over path 120 to network switching function
110 using well-known PSTN or SIP routing methods. To determine
further routing information for the call setup request, network
switching function 110 will issue a query to SIP registrar 111
associated with the call set-up target, such as multi-mode
communication unit 102, using path 130 to obtain the current list
of one or more contacts for multi-mode communication unit 102.
Since multi-mode communication unit 102 is in first network 106 or
the WLAN-mode, the highest-priority contact in the list will
preferably indicate the IP address, number or the like on which
multi-mode communication unit 102 can be reached within the WLAN,
possibly indicating that multi-mode communication unit 102 shall be
reached via the optional proxy 118. Switching function 110 will
then forward a call setup request, typically in the form of a SIP
INVITE message, to multi-mode communication unit 102 via WLAN path
135 using, for example, wireless connection 105. It should be noted
that if optional proxy 118 is being used, the call setup request
can be forwarded via proxy 118, using paths 140 and 145, where path
145 uses wireless connection 105 and path 140 extends from proxy
server 118 to network switching function 110. In accordance with
various alternative exemplary embodiments, SIP registrar 111 can
process call setup routing using registered contacts to forward the
call setup request to multi-mode communication unit 102 according
to the highest priority contact.
[0033] After successful session initiation, the content or bearer
portion of the communication preferably uses path 135 forming a
connection between multi-mode communication unit 102 and network
switching function 110 and path 120 to peer communication unit 114.
Note that if peer communication unit 114 is within first network
106, the content path would not require network switching function
110 once the communication is set up and content can flow directly
between multi-mode communication unit 102 and peer communication
unit 114.
[0034] Referring to FIG. 2, FIG. 3, and FIG. 4, where like
reference numerals refer to like entities, various exemplary states
associated with movement and re-registration will be discussed.
[0035] Initially with reference to FIG. 2, multi-mode communication
unit 102 has moved closer to the edge of the WLAN or LAN, or first
network 106, for example, indicated by a weakening of the strength
of signal 205 associated with the first network and a increasing or
constant strength of signal 207 associated with second network 108.
It will be appreciated that as part of the operation of multi-mode
communication unit 102, a quality factor or metric such as signal
to noise ratio, Received Signal Strength Indicator RSSI, or the
like, may be measured and monitored. Also, the detection of a
border cell associated with, for example, first network 106, and
having a beacon or other signal indicator may provide a warning to
multi-mode communication unit 102 that the "edge" of the network
has been reached. As multi-mode communication unit 102 moves closer
to the boundary of first network 106 it will be determined with
high probability that mode switching into second network 108 may be
imminent or impending. As the result of this determination,
preparation must begin for a re-registration and a mode switch and
possibly a handout for an ongoing call. It will be appreciated that
determination of the probability of an imminent mode switch can be
performed by multi-mode wireless communication unit 102 or another
entity such as proxy server 118, network switching function 110,
Mobility Manager 116, or one of the network entities understood to
be present, by assessing connection quality in the first network
using the quality metric or quality factor described above or a
combination of methods including the rate at which the signal
quality is deteriorating and a comparison with the connection
quality of the wireless connection 107 of second network 108.
[0036] Generally, if the WLAN connection quality level as measured
by signal to noise ratio, frame error rate, fraction of missed ping
messages or other missed messages or responses from multi-mode
communication unit 102, or like assessment, crosses a threshold, a
handover or mode switch is likely. In accordance with some
exemplary embodiments, multi-mode communication unit 102 can use a
hard-wired connection to a LAN, or second network 108. Thus,
detection of an imminent or impending mode switch, e.g. from first
network 106 into second network 108 may include detecting that the
user has removed the connection, or selected an `eject` function,
for example by pushing an eject button or by selecting an eject or
disconnect option from, say, a docking port, cradle, or the like,
via a user interface associated with multi-mode communication unit
102. It will be appreciated that re-registration with a modified
list of contacts, such as with different priorities and expiration
times, affects the way future call setup attempts will be handled.
The contact list can be modified by adding or removing contacts, by
changing priorities of one or more contacts already in the list,
and/or by changing expiration times of contacts already in the
list. Exemplary modifications of a contact list in accordance with
exemplary embodiments are described in detail below. In accordance
with a preferred embodiment, re-registration must be done before
mode switching or handover occurs.
[0037] Re-registration is typically done using a SIP REGISTER
message as noted above with regard to initial contact registration.
If the determination of increased probability of an imminent
mode-switch is performed by multi-mode communication unit 102, the
multi-mode communication unit 102 can re-register with SIP
registrar 111 over wireless connection 105 and using a direct
connection 250, or through proxy server 118 and/or network
switching function 110 through connections 240, 245 and 130. It
should be noted that the determination of increased probability of
an imminent mode-switch can also be performed by proxy server 118,
by Mobility Manager 116 or by network switching function 110, in
which case the entity responsible for the determination also
performs the re-registration on behalf of multi-mode communication
unit 102.
[0038] Referring to FIG. 3, multi-mode communication unit 102 is
shown after a successful re-registration as described above, and
after a mode switch to the second wireless communication network
108. It should be noted that the mode switch will typically involve
a registration with the second wireless communication network 108,
through, for example, MSC 112. If multi-mode communication unit 102
failed to re-register with modified contacts before the mode-switch
occurred, it can re-register with SIP registrar 111 through channel
440 to network switching function 110. It will be appreciated that
such re-registration is only possible if the second network
supports packet data and that, hence, re-registration should
preferably done as described above, as the result of the
determination while multi-mode communication unit 102 is still in
first network 106.
[0039] After re-registration, the call setup request from peer
communication 114 will again be routed on path 120 to network
switching function 110 which again determines how to handle the
call setup request by performing a query over path 130 to SIP
registrar 111 to obtain contact information. It should be noted
that the re-registration shown in FIG. 2 has resulted in a modified
contact list such that the contact with the highest priority will
be associated with or otherwise "point to" second network 108 using
a second network number or second network number address to
identify multi-mode communication unit 102. At that point network
switching function 110 will forward the call setup request via
channel 440 and MSC 112 to multi-mode communication unit 102, using
wireless signal 305.
[0040] Referring to FIG. 4, a scenario is described where
multi-mode communication unit 102 is out of range of both first
network 106 and second network 108. As before, a call setup request
initiated from peer communication unit 114 may be routed on path
120 through network switching function 110 which determines how to
route the call setup request by performing a query over path 130 to
SIP registrar 111 to obtain contact information. An attempt to
reach multi-mode communication unit 102, for example, in second
network 108 will now fail, and call 120 will ultimately be routed
to the lowest priority contact in the registry over channel 441 to
voicemail 450. It will be appreciated that voicemail 450 may be a
voicemail contact inside one of the first and second networks 106,
108 or may be external to both or may alternatively or additionally
be a pager, email, or the like (not shown).
[0041] Multi-mode communication unit 102, having mobility 104, can
move freely within first network 106, or the WLAN or WAN, and may
routinely move out of range, e.g. into second network 108, or the
WAN, and vice versa. If a call or communication is in progress when
movement out of range occurs, a handover, sometimes referred to as
handout when the handover is from the WLAN to the WAN, of the
ongoing communication from first network 106 to second network 108
is required. However, in accordance with the present invention, the
routing of future call set-up requests are of primary interest.
Thus, various inventive techniques and an apparatus providing
advantages in addressing reduction of call set up time after the
determination of an impending mode switch will be the dominant
focus of the balance of the present disclosure.
[0042] As noted briefly herein above, multi-mode communication unit
102 is programmed or configured such that different q-values or
priorities are specified for contacts in a contact list
corresponding to different modes of operation, such as a first set
of q-values when operating in first network 106 and a second set of
q-values when operating in second network 108. To be more specific,
the contact list described above contains addresses for likely
locations where multi-mode communication unit 102 can be reached
such as an address or number for first network 106 and an address
or number for second network 108, and perhaps an address or number
for an external or internal voicemail contact, pager contact, email
contact or the like. Typically an "address" associated with a
contact is a URI as described above, and the "number" is an IP
address or a telephone number. The priority, or q-value, for each
contact will be based on a likelihood that multi-mode communication
unit 102 is reachable at that contact at the time of the attempted
contact. Thus, for example, when multi-mode communication unit 102
is in first network 106, or the WLAN, the contact associated with
first network 106 should have the highest q-value, followed in
priority by the contact associated with second network 108,
followed by an optional, recommended voice mail contact.
[0043] Preferably just before multi-mode communication unit 102
roams out of first network 106 into second network 108, a standard
SIP registration, for example, with SIP registrar 111, may be used
to change priorities and assign the highest q-value to the contact
associated with second network 108. Multi-mode communication unit
102 may optionally remove the contact associated with first network
106, since the validity of the WLAN-assigned IP address associated
with the contact for first network 106 may expire. When multi-mode
communication unit 102 roams back into first network 106, contacts
may be reset using a standard SIP registration as noted above, for
example, with SIP registrar 111. It should be noted that SIP
re-registrations involving a change in the contact list for a
device are generally known. Conventionally, modification of a
contact is explicitly done by a device user or by the device as
part of a logon session of a user, using parameters defining how
the user can be reached at the current location, such as the
current IP address used by the device. In more advanced, but known
implementations, the device may re-register as a result of a change
of attachment point and, for example, modify the IP address in its
contact when it attaches to a new location on a network. However,
it is important to note that such re-registration procedures are
performed after a change in network attachment. In stark contrast,
the present invention allows a modification of a contact list
before a mode switch between networks. The present invention also
allows the modification of the contact list to be triggered by a
determination that an imminent mode switch is likely. The present
invention still further addresses issues associated with operation
at the outer edges of coverage areas where fading in and out of
coverage are likely by, for example, allowing for the specification
of expiration times and modified expiration times, and multiple
address for the same contact as described in greater detail herein
below.
[0044] Based on the use of registration with multiple contacts
having different q-values, network switching function 110, for
example, will try to reach multi-mode communication unit 102 in the
most likely place first through, for example, a query over 130 sent
to SIP registrar 111. If an attempt to reach multi-mode
communication unit 102 in the highest q-value location fails, the
system will try the next, most likely location. Eventually the call
will be routed to the last contact, which is preferably voicemail
or the call set-up attempt will time out or the like.
[0045] By way of an example, which can be shown with reference to
FIG. 1 and FIG. 3, suppose multi-mode communication unit 102 is
initially operating in first network 106 with contacts registered
with SIP registrar 111 as noted above (FIG. 1). A preferable
contact list to be used while operating in the first network
contains a highest-priority contact pointing to the address of
multi-mode communication unit 102 within first network 106; a
lesser priority contact pointing to the number of multi-mode
communication unit 102 within second network 108; and a lowest
priority contact pointing to the voice mail of multi-mode
communication unit 102. Suppose now that the multi-mode
communication unit 102 moves out of first network 106 without
re-registering. Multi-mode communication unit 102 quickly detects
the disappearance of signal 105 associated with the WLAN, or first
network 106, and makes preparations such as bringing up its
cellular stack, which may refer to the protocol stack associated
with operation in second network 108, if not already up (FIG. 3)
and attaching to second network 108 through the use of signaling
messages over wireless connection 107 with switching function 112
of second network 108. Multi-mode communication unit 102 can try to
fix the contacts through registration using packet data but this
may take time or may even be impossible if second network 108 does
not support packet data. If a call is now originated to multi-mode
communication unit 102, network switching function 110 will try to
call multi-mode communication unit 102 using the contact associated
with first network 106 first and the attempt will fail. Network
switching function 110 now tries the next contact, e.g. the contact
with the next highest q-value, which is the number associated with
second network 108 and the call will eventually reach multi-mode
communication unit 102. Such a method, while clearly increasing
availability, significantly increases call setup time.
[0046] While assignment of q-values is standard within SIP,
multi-mode communication unit 102 may advantageously switch
q-values as a function of moving in and out of first network 106
and second network 108 through re-registration in accordance with
various exemplary embodiments. One difficulty in re-registering is
timing re-registrations used by multi-mode communication unit 102
to modify the contacts registered with, for example, SIP registrar
111. For example, when multi-mode communication unit 102 is moving
out of first network 106, a re-registration is preferable. However,
because there is a good chance that multi-mode communication unit
102 will immediately go back into WLAN coverage within first
network 106, and possibly out of coverage of second network 108
multi-mode communication unit 102 may become unreachable if
re-registration occurs too soon. Call setup time becomes long,
because calls will be forwarded to second network 108 before the
contact associated with first network 106 is tried. On the other
hand, if multi-mode communication unit 102 waits until WLAN
coverage drops completely before re-registering, call setup time
may also become long until the re-registration--if at all
possible--will succeed. Moreover, since second network 108 may not
even support packet data, q-values cannot be swapped resulting,
again, in a long call setup time.
[0047] To address these and other issues multi-mode communication
unit 102, while in first network 106, preferably specifies a finite
expiration time for the contact associated with first network 106.
Under such a scenario, multi-mode communication unit 102 must
re-register before the contact expires. If multi-mode communication
unit 102 wanders into second network 108 and cannot send a new
re-registration, the contact associated with first network 106 will
expire and disappear. Before expiration, call setup time would be
long, because the contact associated with first network 106 is
tried first. After expiration of the contact associated with first
network 106, all calls to multi-mode communication unit 102 would
be routed directly to the contact associated with second network
108 thereby improving call setup time. Thus, a short expiration
time for the contact associated with first network 106 improves
call setup times. However, frequent re-registrations required under
the present scenario would present a huge system load and limit the
battery life of multi-mode communication unit 102. Various
exemplary embodiments of the present invention allow the use of a
short expiration time when relevant, while reducing the load of
re-registrations at all other times. It should also be noted that
an expiration time for a contact associated with second network can
be set so as to never expire, or can be set to a high value like
4294967295 seconds or about 136 years. With a high value set for
the expiration time, the contact associated with second network
will remain valid even after, for example, multi-mode communication
unit 102 roams into second network 108 and cannot send a new
re-registration.
[0048] Further in accordance with various exemplary embodiments,
multi-mode communication unit 102 specifies an expiration time for
the contact associated with first network 106 depending on first
network coverage. When such coverage becomes marginal, or when a
border cell is detected via the detection of a beacon signal,
special indication, or the like as noted herein above,
re-registration can be performed and a short expiration time
specified for the contact associated with first network 106. At the
same time, multi-mode communication unit 102 makes preparations for
communication in second network 108, by for example, bringing up
the stack associated with second network 108, such as the cellular
stack, so that future incoming calls can be received. Multi-mode
communication unit 102 then re-registers before expiration of the
newly specified expiration time. If coverage has improved or the
border cell is no longer detected, multi-mode communication unit
102 re-registers with a relatively longer expiration time. If
multi-mode communication unit 102 definitively leaves the coverage
area of first network 106, re-registration with the contact
associated with second network 108 on top, or as the highest
priority or q-value is preferably performed. Such re-registration
however, is not mandatory or urgent, since the contact associated
with first network 106, will soon expire all by itself. Still
further, with regard to priority values and expiration time values,
it will be appreciated that a null value, or a failure to specify a
priority value or expiration time value may advantageously result
in a default value being used. Thus, a failure to provide a setting
may, in itself, be an affirmative setting since allowing a default
value to be used in certain circumstances may enhance performance
in accordance with various exemplary embodiments.
[0049] It should be understood that in referring to priorities,
q-values, and the like, a relative priority between at least two
contacts is also being referred to. For example, a first priority
with a 0.9 value and a second priority with a 0.8 value results in
a relative priority where the first priority is higher than the
second priority. Further, the relative priority can be discussed
with reference to a particular contact. In the example above, a
relative priority of the first contact is higher than the second
contact while a relative priority of the second contact is lower
than the first contact and so on. While in some instances it may be
convenient to describe a first priority as being lowered or raised,
for example relative to a second priority, one of ordinary skill in
the art will appreciate that the same result can be achieved by
raising or lowering the second priority relative to the first
priority, or a combination of both raising or lowering the first
priority and lowering or raising the second priority for example to
achieve the desired relative priority.
[0050] An example of the type of contact list passed during
registration associated with good coverage in the WLAN or first
network 106 is shown in Table 1.
1TABLE 1 Contact Priority Expiration LAN contact q = 0.9 1800 (30
minutes) (IP address in first network 106) Cellular contact q = 0.8
4294967295 (never (cellular phone number expires) in second network
108) Voicemail contact q = 0.1 4294967295
[0051] An example of a contact list, with priorities and expiration
times used for re-registration when multi-mode communication unit
102 detects a border cell or waning coverage in first network 106
is shown in Table 2.
2 TABLE 2 Contact Priority Expiration LAN contact q = 0.9 120 (2
minutes) Cellular contact q = 0.8 4294967295 Voicemail contact q =
0.1 4294967295
[0052] Assuming that multi-mode communication unit 102 looses
coverage associated with first network 106, after, for example, 1
minute and enters the coverage area associated with second network
108, the state of the contacts after an additional 1 minute, e.g.
after the expiration of the contact associated with first network
106 is shown in Table 3.
3 TABLE 3 Contact Priority Expiration LAN contact EXPIRED Cellular
contact q = 0.8 4294967295 Voicemail contact q = 0.1 4294967295
[0053] It should be noted that the contact expiration time for the
contact associated with first network 106 can be made to depend on
the quality of the coverage and the `speed` of multi-mode
communication unit 102. As coverage quality goes down or if speed
goes up, multi-mode communication unit 102 preferably uses a
shorter expiration time for the contact associated with first
network 106. Speed as used herein above can be derived from the
amount of inertial acceleration as detected through, for example, a
gyroscope and/or an accelerometer; a GPS determined speed, the
number of access points recently visited, or the rate at which
coverage quality changes.
[0054] In accordance with various alternative exemplary
embodiments, under certain conditions multi-mode communication unit
102 may move back and forth between good, marginal and no coverage
in, for example, first network 106 giving rise to frequent
re-registration as described herein above. To avoid numerous
re-registrations, many of which are to be made from marginal
coverage giving rise to a higher expense in terms of transmission
power or the like, multi-mode communication unit 102 can add a
third contact in the form of a second contact for first network 106
as shown in Table 4.
4TABLE 4 Contact Priority Expiration LAN contact A q = 0.9 expires
120 (IP address in first network 106) Cellular contact q = 0.8
4294967295 (cellular phone number in second network 108) LAN
contact B q = 0.7 expires 3600 (1 (IP address in first network 106)
hour) Voicemail contact q = 0.1 4294967295
[0055] With contacts arranged as noted in Table 4, if the
short-lived contact A for first network 106 expires and multi-mode
communication unit 102 does not manage to re-register in time, the
system will still find multi-mode communication unit 102 in first
network 106 if a call routed to multi-mode communication unit 102
according to the contact associated with second network 108 does
not succeed. The above described variation can be called a `contact
sandwich` because the cellular contact is sandwiched between two
WLAN contacts. It should be noted that in accordance with relevant
protocols, SIP registrar 111 will not accept two equal contact
addresses. Accordingly, WLAN contacts A and B must be different but
they must still terminate at multi-mode communication unit 102. To
overcome such a limitation, first network 106 may uniquely identify
multi-mode communication unit 102 using a single or multiple IP
addresses for the same unit using the constructs shown in Table
5.
5 TABLE 5 LAN contact a = default@<IP_address> LAN contact b
= backup@<IP_address>
[0056] While SIP registrar 111 does not allow the use of multiple
contacts with the same address, it does support the specification
of multiple contacts with equal q-values. As per the SIP
specification, contacts with equal q-values will preferably be made
to ring at the same time and the first contact to pick up will get
the call. If neither equal q-valued contact picks up the call, the
system will try the contact with the next lower q-value such as
voicemail or the like. Simultaneous ringing however has a
disadvantage in that it may use resources such as cellular paging
to contact, for example, multi-mode communication unit 102, which
may not even be in the cellular network. PBX CPU and trunk
resources associated, for example, with network switching function
110, may also be unnecessarily burdened because the network
switching function 110 must set up a cellular call in second
network 108 and a call in the enterprise in first network 106 for
each call that is being made to multi-mode communication unit 102.
Thus, in accordance with various exemplary embodiments,
simultaneous ringing is used in a more dynamic manner as further
described herein below.
[0057] For normal operation in first network 106, multi-mode
communication unit 102 specifies contacts with different q-values
for ordered ringing as described above and shown in Table 1. When
multi-mode communication unit 102, which may currently be operating
in first network 106 or second network 108, detects entry into an
area having marginal coverage, or when it detects a border cell,
multi-mode communication unit 102 starts preparations such as
bringing up a stack associated with second network 108 and
re-registers, specifying simultaneous ringing for the contacts
associated with first and second network 106, 108 as shown in Table
6.
6 TABLE 6 Contact Priority Expiration LAN contact q = 0.8 1800 (30
minutes) Cellular contact q = 0.8 4294967295 Voicemail contact q =
0.1 4294967295
[0058] When a call is placed to multi-mode communication unit 102,
the system will simultaneously ring the contacts associated with
the first and second networks 106 and 108. If possible, multi-mode
communication unit 102 will answer the call on first network 106
and if coverage is very bad, it will answer on second network 108.
Naturally, if coverage is absent for first network 106, multi-mode
communication unit 102 will only receive the call on second network
108. It should be noted that operation as described may rely on,
for example, a user interface which can present different ringing
options such as providing one ringing indication for calls to
multi-mode communication unit 102 on first network 106 and another,
ringing indication for calls to multi-mode communication unit 102
on second network 108. Alternatively and preferably, the choice of
the network that will be used for the call may be made by the
communication unit and may be made in a way that is transparent to
the user. In either case, call setup times are short, while, if
multi-mode communication unit 102 does not pick up, the call will
still be routed to the next-lower priority contact such as
voicemail, within a reasonable amount of time. It should also be
noted that when multi-mode communication unit 102 returns into good
coverage associated with first network 106, or when it no longer
detects a border cell, the normal contacts associated with ordered
ringing are preferably restored through re-registration, for
example, using the list from Table 1. Further, when multi-mode
communication unit 102 gets "stuck" in second network 108, without
coverage associated with first network 106, it preferably
re-registers with a set of contacts normally associated with
cellular operation. Such re-registration in a cellular only
environment may be accomplished using SIP-over-packet data. It will
be appreciated that, alternatively, multi-mode communication unit
102 can also do nothing and wait for the contact associated with
first network 106 to expire. It will also be appreciated that
various combinations of the above described scenarios may be used
without departing from the invention.
[0059] Referring to FIG. 5, a simplified block diagram of
multi-mode communication unit 102 arranged for reducing call set up
time in accordance with various exemplary embodiments will be
discussed and described. Multi-mode communication unit 102 is
generally known other than the modifications and improvements
disclosed herein. Thus the known functions and structure of such
devices will not be described in detail other than as related to
the inventive principles and concepts disclosed and discussed
below. Multi-mode communication unit 102 includes an antenna 501 or
antenna structure that operates to couple radio frequency (RF)
signals between a transceiver or RF interface 503 and the first or
second network 106, 108 as is known. For example, radio signals
transmitted from the WLAN, or first network 106 or Wireless WAN
108, such as respectively, by an access point or base transmitter
site are absorbed by antenna 501 and coupled to a receiver portion
of transceiver 503.
[0060] Respectively, signals amplified by and coupled from
transceiver 503, specifically a transmitter such as a WLAN
transmitter 509 or a WAN transmitter 511, to antenna 501 are
radiated or transmitted or sent to the access point or base
transmitter site according to known WLAN technologies, such as
802.11 and other technologies described herein above. Transceiver
503 will preferably be configurable to support simultaneous air
interfaces with multiple communication networks according to the
conventions and protocols of each or may alternatively further
include one or more of a WLAN transceiver 509 and WAN transceiver
511 for such purposes as will be appreciated by those of ordinary
skill. Transceiver 503 or respective receivers and transmitters are
coupled or interconnected as depicted and interactively operate
with and are controlled by a controller 505 to provide to, or
accept or receive from the controller 505, voice traffic or data
messages or signals corresponding thereto in packet data or circuit
form. It should be noted that if multi-mode communication unit 102
uses a hardwired interface to connect to the LAN, it will
preferably have a network interface function (not shown), similar
or equal to, for example, interface 603 (see FIG. 6) described in
greater detail herein below.
[0061] Accordingly, transceiver 503 as controlled by and in
cooperation with the controller 505 and functions thereof provide
multi-mode communication unit 102 with multi or dual operating mode
capability. More particularly, multi-mode communication unit 102 is
capable of registering with and obtaining service from first and
second communication networks 106 and 108. For purposes of
simplifying this disclosure, the balance of the discussion will
refer to only the transceiver 503 and it is understood the
transceiver with the controller 505 has the capability to establish
and maintain a connection via either of or both the first and the
second networks 106, 108.
[0062] Controller 505 is coupled to and generally operates in a
known manner with a user interface 507 providing, in certain cases,
operating indicia such as ringing and the like for each network
capable of being connected with. User interface 507 is known and
typically includes, for example, audio transducers, such as an
earphone or speaker and microphone, a display and a keypad. The
transceiver and user interface are each inter coupled, as depicted
to the controller 505 and the controller provides overall
operational command and control for multi-mode communication unit
102. It should be noted that controller 505 is essentially a
general-purpose processor and, preferably, includes processor 513
and associated memory 515. Processor 513 is, preferably, a known
processor based element with functionality that will depend on the
specifics of the air interfaces with the first and second networks
106 and 108 as well as various network protocols for voice and data
traffic. Processor 513 will operate to encode and decode voice and
data messages to provide signals suitable for the transceiver, a
transducer, or further processing by the controller 505. Processor
513 may include one or more generally available microprocessors,
digital signal processors, and other integrated circuits depending
on the responsibilities of the controller 505 with respect to
signal processing duties or other unit features not here
relevant.
[0063] Controller 505 also includes memory 515 that may be, for
example, a combination of known RAM (Random Access Memory), ROM
(Read-Only Memory), EEPROM (Electrically Erasable Programmable ROM)
or magnetic memory. Memory 515 is used to store among various other
items or programs etc., an operating system or software, data, and
variables 517 for execution or use by the processor 513. Operating
software 517, when executed by the processor 513, will result in
the processor performing the requisite functions of multi-mode
communication unit 102 such as interfacing with user interface 507
and transceiver 503 or transmitting and receiving devices. Memory
515 further includes call processing routines not specifically
shown for supporting voice and data calls that will be appreciated
by one of ordinary skill and that will vary depending on air
interface, call processing, and service provider or network
specifics.
[0064] As depicted, memory 515 further includes, in some
embodiments, a signal quality assessment routine 519 for use in
determining whether a handover or a mode switch may be required if
multi-mode communication unit 102 is responsible for that
determination as discussed herein above and to assess signal
quality and perform threshold comparison. Depending on the result,
signal quality assessment routine 519 may determine the probability
that a mode switch or handover situation is imminent and compare
that probability with a predetermined threshold. The exact nature
of signal quality assessment routine 519 may be communication unit
specific and can be experimentally determined and modified as
experience dictates. As noted above, signal quality assessment
routine 519 may be a signal to noise determination, an RSSI
determination, a frame error rate determination, a ping response
failure, or other determination resulting in a quality factor. As
will be appreciated, the quality factor may be compared against a
threshold and, if above or below the threshold, a threshold
condition associated with the quality factor will be deemed to
exist.
[0065] In one embodiment, SIP messaging routines 521 are provided
for generating and responding to SIP messages according to known
techniques and may be used to support the air interface with first
and second communication networks 106 and 108 to initiate and
receive calls, register and re-register contacts, and the like.
Also depicted is a voice conversion or vocoder routine 523 which
may be used in conjunction with other specialized portions of
processor 513 to convert voice to digital form and digital voice to
a form that can be reproduced in an audio format for use in driving
a speaker or earpiece. Additionally, packet data processes 525 are
provided for formulating appropriate packets for transport
according to the specifics of the communication networks.
[0066] As noted above, various data is provided in memory 515, and
specifically, unit information 527 may be provided including
identification information used to identify multi-mode
communication unit 102 such as phone numbers, IP addresses and/or
URIs. Call information 529 may also be stored in memory 515 for
tracking information associated with calls. Collectively the
information stored in memory 515 can be used to identify a
particular unit and a particular call, should a mode switch or a
handover or handout be required. Contact information 531, as
described in detail herein above may also be stored in memory 515
and may be used for SIP registration and re-registration, for
example, with SIP registrar 111. Various other routines 533 not
especially relevant to the disclosure and that will be obvious to
one of ordinary skill given a specific communication unit will not
be discussed.
[0067] As noted above, in some embodiments, first network 106 is a
wireless local area network and second network 108 is a wireless
wide area network. Multi-mode communication unit 102, specifically
controller 505 operating with transceiver 503 can obtain call
information during call setup. If, for example, first network 106
uses SIP messaging for call setup, a Session Initiation Protocol
(SIP) INVITE message and a response message to the SIP INVITE
message will be exchanged depending on which party initiates call
set up.
[0068] Referring to FIG. 6, a simplified block diagram of
infrastructure component 605 capable of implementing functions such
as network switching function 110 will be discussed. It will be
appreciated that in a manner similar to FIG. 5, a general purpose
computing platform embodying a stand alone infrastructure component
can be viewed as another of various network entities, such as proxy
server 118 with emphasis on SIP registration and call set up.
Generally, infrastructure component 605 includes an interface 603,
specifically a network interface function, such as a network
transceiver, RF interface or the like, or a software interface
function if infrastructure component 605 is operating on a platform
also embodying another network entity. It will be appreciated that
network interface 603 can, in accordance with some embodiments, be
an RJ-45 physical connector and support an Ethernet protocol, an IP
protocol, a cellular protocol and/or a PSTN protocol.
[0069] The interface 603 is coupled to and controlled by a
controller 605 that can be further coupled to a local or remote
operator interface, such as a monitor and keyboard or another
computing platform all as known. The controller includes a
processor 613 that is a general purpose processor that may be
redundant for incremental network availability. The processor is
coupled to a memory 615 that will be some combination of RAM, ROM,
EEPROM, and likely magnetic based memory as would be expected on
such platforms. Note a suitable platform, server, or computer is
available from various manufacturers, including IBM, Dell, and
Hewlett Packard, for example.
[0070] Memory 615 includes an operating system, data, and variables
617 that provide the general operating conditions, etc. for the
processor as is known. Memory 615 may also contain contact list
information obtained via, for example, a query to SIP registrar 111
for contacts used to route call set ups. In some embodiments SIP
messaging routines 619 are included to facilitate forming and
decoding messages according to known SIP protocols. Additionally
packet data processing routines 621 are provided for supporting
packet data communication within the network according to the
conventions used by the network. Note as discussed above
identification such as caller IDs, called party IDs, Call IDs, and
the like are used to distinguish one call from another. Ongoing
communication or call information 625 obtained as discussed above
for ongoing calls may be stored. If infrastructure component 605 is
responsible for determining when a mode switch may be imminent, a
signal quality assessment routine 627, operating as noted above
will be provided to determine a quality factor or the probability
of or need for a switch from operation in accordance with the first
mode of operation to operation in accordance with the second mode
of operation. As also noted, signal quality assessment routine 627
may be a signal to noise determination, an RSSI determination, a
frame error rate determination, a ping response failure, or other
determination resulting in a quality factor. As will be
appreciated, the quality factor may be compared against a threshold
and, if above or below the threshold, a threshold condition
associated with the quality factor will be deemed to exist.
Furthermore, communication unit states 629 are stored for all
communication units being serviced to allow infrastructure
component 605 to formulate and respond to SIP messages on behalf of
such units. Additionally, many other routines 631 understood by
those of ordinary skill may be present though not necessarily
relevant.
[0071] Referring to FIG. 7, a simplified block diagram of SIP
registrar 705 capable of implementing SIP related functions in
conjunction with network entities such as network switching
function 110 will be discussed. It will be appreciated that in a
manner similar to FIG. 5 and FIG. 6, a general purpose computing
platform embodying a stand alone SIP registrar can be viewed as
another of various network entities, such as proxy server 118 with
emphasis on SIP registration and call set up. Generally, SIP
registrar 705 includes an interface 703, specifically a network
interface function, such as a network transceiver, RF interface or
the like, or a software interface function if SIP registrar 705 is
operating on a platform also embodying another network entity, such
as the network switching function 110 or a 3G Home Location
Register (HLR). It will be appreciated that network interface 703
can, in accordance with some embodiments, be an RJ-45 physical
connector and support an Ethernet protocol or another LAN or WAN
protocol.
[0072] Interface 703 is coupled to and controlled by controller 705
that can be further coupled to a local or remote operator interface
707, such as a monitor and keyboard or another computing platform
all as known. The controller includes processor 713 that is a
general purpose processor that may be redundant for incremental
network availability. Processor 713 is coupled to memory 715
including some combination of RAM, ROM, EEPROM, and likely magnetic
based memory as would be expected on such platforms. Memory 715
includes an operating system, data, and variables 717 providing
general operating conditions, and the like, for processor 713 as is
known. In some embodiments, SIP messaging routines 719 are included
to facilitate forming and decoding messages according to known SIP
protocols. Additionally packet data processing routines 721 are
provided for supporting packet data communication within the
network according to the conventions used by the network. Note as
discussed above identification such as caller IDs, called party
IDs, Call IDs, and the like may be used to distinguish one call
from another, if needed. To provide SIP registration functionality
in accordance with various exemplary embodiments, contact registry
723 may be used to contain contact information including an
address, such as an internet address or telephone number, priority
or q-value information, and an expiration time for the contact.
According to known SIP protocols, a SIP REGISTER message can be
used to enter and modify the contact information 713. The contact
information 713 can be queried in various ways including a standard
query language message or by using a SIP INVITE message.
Additionally, many other routines 731 understood by those of
ordinary skill may be present though not necessarily relevant.
[0073] Referring to FIG. 8, a flow chart illustrating an exemplary
registration procedure pursuant, for example, to reducing call set
up times will be discussed and described. The method of FIG. 8 is
advantageously practiced, for example, when multi-mode
communication unit 102 is in an area of marginal coverage or
detects a border cell as described herein above. After start at
801, multi-mode communication unit 102 registers at 802, for
example, with SIP registrar 111, different priorities associated
with different contacts capable of providing contact to multi-mode
communication unit 102 within first network 106, second network
108, or out of both networks, such as voicemail as described herein
above and shown, for example, in Table 1. If, for example,
multi-mode communication unit 102 is operating in first network
106, and marginal coverage is detected at 803, priorities may be
re-registered at 804 with the priorities for the contact associated
with first network 106 and second network 108 set to be equal as
noted for example, in Table 6 above and this will result, for
example, in simultaneous ringing in both networks. Multi-mode
communication unit 102 can provide a separate indication associated
with ringing on each network allowing a user to choose the network
to pick up on, or, if coverage for one of the networks is
sufficiently poor, only the network with coverage will ring
through. Once priorities are re-registered with equal values,
preparations are made, e.g. the stack can be brought up for second
network 108 and the communication unit can attach to the second
network 108 in preparation for operation therein at 805. It should
be noted that if marginal coverage is not detected at 803,
registration of different priorities and expiration times will have
been completed and the procedure can end, stop, wait or the like,
or alternatively, marginal coverage or border cells can be checked
for periodically, e.g. after a predetermined time interval has
elapsed. Also, after the new stack is brought up at 805,
registration, for example, at 802, can be made with the new network
if a mode switch occurs, otherwise, marginal coverage or border
cells may be checked for within the existing network and, if
marginal coverage or border cells are no longer detected,
suggesting, for example, that a mode switch has not occurred or is
not imminent, priorities can be reset to original values as
described above, or the like (not shown).
[0074] Referring to FIG. 9, a flow chart illustrating another
exemplary registration and operation procedure that may be used,
for example, in marginal coverage areas or border cells is
described. After start at 901, multi-mode communication unit 102
registers at 902, for example, with SIP registrar 111, different
priorities associated with different contacts capable of providing
contact to multi-mode communication unit 102 within first network
106, second network 108, or out of both networks, such as voicemail
as just described, for example, with reference to FIG. 8 above. If,
for example, multi-mode communication unit 102 is operating in
first network 106, and marginal coverage or a border cell is
detected at 903, one or more expiration times may be shortened at
904, for example, for the contact associated with first network
106. This way, if multi-mode communication unit 102 loses coverage
in first network 106, the contact will expire more quickly so that
contact can be made more quickly in second network 108, which is
where multi-mode communication unit 102 will most likely be
operating. Also in preparation for losing contact with network 106,
the protocol stack for operation in second network 108 may be
brought up at 905 or, if already up, multi-mode communication unit
102 may attach to second network 108 by, for example, exchanging
messages with the network switching function of the second network
108, like the MSC 112. Coverage may be checked again at 906, for
example, prior to expiration of the shorter expiration time
associated with the contact for first network 106, and if the first
network coverage has strengthened or a border cell is no longer
detected, contacts may be re-registered with longer expiration
times at 907. If very weak coverage or a border cell is detected at
906, multi-mode communication unit 102 re-registers with the
contact associated with second network 108 at the top priority.
[0075] It should be noted that the methods and apparatus described
above for reduction of call setup time may be implemented in
reverse or with different communications networks than those
discussed above. For example, the first wireless communications
network may be the cellular WAN and second network 108 may be the
WLAN. The multi-mode communication unit then operates in WAN and
when the communications device detects an action preparatory to
making a call over the cellular WAN, registers with and brings up
the stack for the WLAN. It should also be noted that the methods of
FIG. 8 and FIG. 9 while explained in terms of the various systems
and apparatus introduced and discussed above, can as well be
practiced by other systems and units provided the concepts and
principles described and disclosed can be implemented by such
systems and units.
[0076] Thus various systems and apparatus have been disclosed and
described that implement various principles and concepts that
provide for a reduction in call setup times among other
advantages.
[0077] This disclosure is intended to explain how to fashion and
use various embodiments in accordance with the invention rather
than to limit the true, intended, and fair scope and spirit
thereof. The invention is defined solely by the appended claims, as
they may be amended during the pendency of this application for
patent, and all equivalents thereof. The foregoing description is
not intended to be exhaustive or to limit the invention to the
precise form disclosed. Modifications or variations are possible in
light of the above teachings. The embodiment(s) was chosen and
described to provide the best illustration of the principles of the
invention and its practical application, and to enable one of
ordinary skill in the art to utilize the invention in various
embodiments and with various modifications as are suited to the
particular use contemplated. All such modifications and variations
are within the scope of the invention as determined by the appended
claims, as may be amended during the pendency of this application
for patent, and all equivalents thereof, when interpreted in
accordance with the breadth to which they are fairly, legally, and
equitably entitled.
* * * * *
References